As a piston-cylinder type damper of this type, one based on pneumatic action is proposed in Japanese patent Public Disclosure No. SHO 58-174038.
In this damper, the piston rod is elongated with respect to the cylinder when the loading table projects out of the player. Also, the negative pressure produced in the head chamber in the cylinder is used to control the quantity of air taken into the chamber, thus effecting braking by means of the action of the negative pressure. Furthermore, when returning the open door or the projected table, the piston rod is pushed into the cylinder, so that air in the head chamber of the cylinder is quickly exhausted to the outside when the piston rod is pushed.
In the above piston-cylinder type air damper, when the maximum volume of the head chamber of the cylinder is constant and the flow rate of air taken into the head chamber at the time of the elongation of the piston rod is constant, the braking power is constant, so that it is impossible to vary the size of the braking force depending upon the purpose of use.
Therefore, it is necessary to control the diameter of the cylinder or the rate of flow of the air taken into the head chamber at the time of the elongation of the piston rod depending upon the use, and the design has to be altered for each purpose.